/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package arq.cmdline;

import jena.cmd.ModBase;

import org.apache.jena.query.Dataset ;
import org.apache.jena.sparql.core.DatasetGraph ;

public abstract class ModDataset extends ModBase
{
    protected boolean createAttempted = false ;
    protected Dataset dataset = null ;
    
    public ModDataset() {}
    
    final
    public Dataset getDataset() { 
        if ( ! createAttempted )
            dataset = createDataset() ;
        createAttempted = true ;
        return dataset ;
    }
    
    public DatasetGraph getDatasetGraph() {
        Dataset ds = getDataset() ;
        if ( ds == null )
            return null ;
        return ds.asDatasetGraph() ;
    }

    public abstract Dataset createDataset() ; 
}
